import java.util.Scanner;

public class Fib {
//循环
   /* public static int  fib(int n){
        if(n == 1 || n == 2){
            return 1;
        }
        int f1 = 1;
        int f2 = 1;
        int f3 = 0;
        for (int i = 3; i <= n; i++) {
            f3 = f1 + f2;
            f1 = f2;
            f2 = f3;
        }
        return f3;
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个数 :");
        int n = sc.nextInt();
        int ret = fib(n);
        System.out.println(ret);
    }*/
    //迭代
    public static int  fib(int n){
        if(n == 1 || n == 2){
            return 1;
        }
        return fib(n-1)+fib(n-2);

    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入一个数 :");
        int n = sc.nextInt();
        int ret = fib(n);
        System.out.println(ret);
    }
}
